The present invention is intended for the real time tracking of individual objects within a cluster of objects at a range of several hundred kilometers with a resolution of a meter or less. Conventional radars are not accurate enough to provide these capabilities, and an interferometer based system is the only technology available today that can potentially provide the necessary resolution for such an application. Broad baseline interferometer systems have long been used in radio astronomy to accurately determine the position of distant objects in deep space, and have provided better resolution than could be obtained using optical techniques.
A radar interferometer system includes two or more antennas located at some distance from each other. Each of the antennas receives the same signal reflected from a given object, but with different phase angles and time delays. By measuring these phase and time differences, one can get extremely high angular accuracies, depending on the distance of separation (baseline) of the different receiving antennas. In radio astronomy, baselines as large as the earth itself have been used. The present invention contemplates baselines on the order of 500 meters.
The interferometers used in radio astronomy are primarily used to accurately determine the positions of very distant objects. In such systems response time is not a limiting factor, i.e., the signals can be recorded on magnetic tape for later analysis. In the case of real time tracking systems, however, response time is a very important consideration. One of the major problems of using the signal handling as taught in the prior art is that the time required to do the signal processing would be too long to permit real time tracking of a plurality of objects.
It is therefore an object of the present invention to provide an interferometer based radar system with improved signal handling capabilities so that the signals from individual objects in a cluster can be processed in real time.
It is another object of this invention to provide high enough resolution to be able to distinguish between individual objects of a cluster and to determine the three-dimensional positions of the individual objects.